Dynamic analysis system

ABSTRACT

A dynamic analysis system includes an imaging unit, an attenuation process unit and an analysis unit. The imaging unit images a dynamic state of a subject, thereby generating a plurality of frame images showing the dynamic state of the subject. The attenuation process unit performs an attenuation process to attenuate an image signal component of a product in the frame images. The analysis unit analyzes the dynamic state of the subject based on the frame images after the attenuation process.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation under 35 U.S.C. § 120 of Ser. No.15/159,152, filed May 19, 2016, which is incorporated herein referenceand which claimed priority to Japanese Application No. 2015-105322,filed May 25, 2015. The present application likewise claims priorityunder 35 U.S.C. § 119 to Japanese Application No. 2015-105322, filed May25, 2015, the entire content of which is also incorporated herein byreference.

FIELD OF THE INVENTION

The present invention relates to a dynamic analysis system.

DESCRIPTION OF THE RELATED ART

With the advent of dynamic FPDs (Flat Panel Detectors), there has beenproposed a method of: performing continuous X-ray imaging on a site of ahuman body to be diagnosed, thereby imaging a dynamic state of the site;and analyzing a function of the site. (Refer to, for example, JapanesePatent Application Publication No. 2004-312434.)

There has also been proposed generating, as diagnostic supportinformation, a characteristic amount related to a function of a dynamicstate, such as the ventilation function or the bloodstream function,based on a series of frame images obtained by dynamic imaging. (Referto, for example, International Patent Application Publication No.2009/090894.)

By the way, during or after surgeries, patients are often connected tomedical tubes such as central venous catheters and drainage tubes (shownin FIG. 8). When dynamic X-ray imaging of the chests of these patientswho are subjects is performed, and dynamic analysis is performed on theobtained dynamic images, movements of products such as medical tubesaccompanying body movement, pulsation and/or respiration of the patientsbecome artifacts in the analysis results. In particular, in diagnosisduring or after surgeries, the analysis results are often compared withanalysis results of images of the patients taken before the surgeries ina state in which no products such as medical tubes are attached to thepatients or, as follow-up, compared with analysis results of images ofthe patients taken in the past. If products such as medical tubes arecaptured, it is difficult to determine whether difference between theanalysis results shows change in the state(s) of the patients or showspresence/absence of products such as medical tubes. Similarly, productssuch as pacemakers, implantable cardiac defibrillators, and metallicplates, screws and bolts to fix broken collarbone, ribs and vertebraealso become artifacts in the analysis results if move accompanying bodymovement, pulsation and/or respiration of patients.

BRIEF SUMMARY OF THE INVENTION

Objects of the present invention include improving diagnostic accuracybased on analysis results of dynamic images.

In order to achieve at least one of the objects, according to an aspectof the present invention, there is provided A dynamic analysis systemincluding: an imaging unit which images a dynamic state of a subject,thereby generating a plurality of frame images showing the dynamic stateof the subject; an attenuation process unit which performs anattenuation process to attenuate an image signal component of a productin the frame images; and an analysis unit which analyzes the dynamicstate of the subject based on the frame images after the attenuationprocess.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

The present invention is fully understood from the detailed descriptiongiven hereinafter and the accompanying drawings, which are given by wayof illustration only and thus are not intended to limit the presentinvention, wherein:

FIG. 1 shows the overall configuration of a dynamic analysis systemaccording to an embodiment of the present invention;

FIG. 2 is a block diagram showing the functional configuration of aconsole shown in FIG. 1;

FIG. 3 is a flowchart showing an imaging control process performed by acontrol unit shown in FIG. 2;

FIG. 4 is a flowchart showing a dynamic analysis process performed bythe control unit shown in FIG. 2;

FIG. 5 is a flowchart showing a product attenuation process performed atStep S11 shown in FIG. 4;

FIG. 6 schematically shows a density profile of a product region in across-sectional direction and correction thereof;

FIG. 7A shows a state, viewed from the top, in which a radiationgeneration apparatus emits laser beams to, of a subject, a pointcorresponding to an isocenter and a range within which tomographicimages are generated by a reconstruction process;

FIG. 7B shows the state in FIG. 7A from a side opposite to a side wherethe radiation generation apparatus is disposed;

FIG. 7C shows the subject in the state in FIG. 7A from the side wherethe radiation generation apparatus is disposed; and

FIG. 8 shows an example of an image of a chest to which products areattached.

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, preferred embodiments of the present invention aredescribed with reference to the drawings. However, the present inventionis not limited thereto.

First Embodiment

(Configuration of Dynamic Analysis System 100)

First, the configuration of a first embodiment of the present inventionis described.

FIG. 1 shows an example of the overall configuration of a dynamicanalysis system 100 of the embodiment.

The dynamic analysis system 100 is, for example, a visiting system forimaging patients who cannot move easily because they are in surgeries,after surgeries or the like, and includes a radiation generationapparatus 1, a console 2, an access point 3 and an FPD (Flat PanelDetector) cassette 4. The radiation generation apparatus 1 has wheelsand is configured as a movable visiting cart provided with the console 2and the access point 3. In the dynamic analysis system 100, the console2 is communicable/connectable with the radiation generation apparatus 1and the FPD cassette 4 via the access point 3.

As shown in FIG. 1, the dynamic analysis system 100 is brought into asurgery room, an intensive care unit (ICU), a hospital's ward Rc or thelike and performs dynamic imaging of a subject H therein by emittingradiation from a portable radiation source 11 of the radiationgeneration apparatus 1 in a state in which the FPD cassette 4 isinserted, for example, into between (i) the subject H lying on a bed Band (ii) the bad B or into a not-shown insertion slot provided on a sideof the bed B opposite to the side where the subject H lies.

Dynamic imaging means obtaining a plurality of images of a subject H byrepeatedly emitting pulsed radiation such as pulsed X-rays atpredetermined time intervals (i.e., pulse emission) to the subject H orcontinuously emitting radiation such as X-rays at a low dose ratewithout a break (i.e., continuous emission) to the subject H. By dynamicimaging, a cyclic dynamic state of a subject H is imaged. Examples ofthe cyclic dynamic state include: shape change of the lung, i.e.,expansion and contraction of the lung, accompanying respiration (i.e.,breathing); and pulsation of the heart. A series of images obtained bythis continuous imaging is called a dynamic image. The imagesconstituting a dynamic image are called frame images.

In the embodiment, the dynamic analysis system 100 images the chest of asubject H, thereby imaging its dynamic state. However, the imaging siteis not limited thereto.

Hereinafter, apparatuses or the like constituting the dynamic analysissystem 100 are described.

The radiation generation apparatus 1 can perform at least one of pulseemission and continuous emission. The radiation generation apparatus 1includes the radiation source 11, a radiation emission control unit 12and an exposure switch 13.

The radiation source 11 emits radiation (e.g., X-rays) to a subject Hunder the control of the radiation emission control unit 12.

The radiation emission control unit 12 controls the radiation source 11based on radiation emission conditions sent from the console 2 so as toperform radiography. The radiation emission conditions input from theconsole 2 include, for example, a tube current, a tube voltage, a framerate (i.e., the number of frame images taken per unit time (e.g., onesecond), total imaging time for each imaging or the total number offrame images taken by each imaging, type of an added filter and, in thecase of pulse emission, radiation emission time for each frame image.

The exposure switch 13 inputs radiation emission command signals to theconsole 2 by being pressed.

The console 2 outputs the radiation emission conditions to the radiationgeneration apparatus 1 and outputs image reading conditions to the FPDcassette 4 so as to control radiography and reading of radiographs,performs preview display of image data sent from the FPD cassette 4, andanalyzes the image data so as to calculate characteristic amountsrelated to a ventilation function and a bloodstream function of thelung.

FIG. 2 shows an example of the functional configuration of the console2. As shown in FIG. 2, the console 2 includes a control unit 21, astorage unit 22, an operation unit 23, a display unit 24, acommunication unit 25 and a connector 26. These components are connectedto one another via a bus 27.

The control unit 21 includes a CPU (Central Processing Unit) and a RAM(Random Access Memory). The CPU of the control unit 21 reads a systemprogram and various process programs stored in the storage unit 22 inresponse to operations through the operation unit 23, opens the readprograms in the RAM and performs various processes such as thebelow-described imaging control process and dynamic analysis process inaccordance with the opened programs, thereby performing concentratedcontrol of actions of the components of the console 2, the radiationgeneration apparatus 1 and the FPD cassette 4. The control unit 21functions as an attenuation process unit, an analysis unit and arecognition unit.

The storage unit 22 is constituted of a nonvolatile semiconductormemory, a hard disk and/or the like. The storage unit 22 stores thereinvarious programs to be executed by the control unit 21, parametersnecessary to perform processes in accordance with the programs, and datasuch as process results. For example, the storage unit 22 stores thereina program to perform the imaging control process shown in FIG. 3 and aprogram to perform the dynamic analysis process shown in FIG. 4. Thesevarious programs are stored in the form of a readable program code(s),and the control unit 21 acts following the program code(s).

The storage unit 22 also stores therein the radiation emissionconditions and the image reading conditions for dynamic imaging. Theradiation emission conditions and the image reading conditions can beset by a user operating the operation unit 23.

The storage unit 22 also stores therein image data sent from the FPDcassette 4 correlated with patient information on subjects H, analysisresults calculated based on the image data, and so forth.

The operation unit 23 includes: a keyboard including cursor keys, numberinput keys and various function keys; and a pointing device such as amouse, and outputs, to the control unit 21, command signals inputthrough key operations to the keyboard and mouse operations. Theoperation unit 23 may be provided with a touch panel on a display screenof the display unit 24. In this case, the operation unit 23 outputscommand signals input through the touch panel to the control unit 21.

The display unit 24 is constituted of a monitor such as an LCD (LiquidCrystal Display) or a CRT (Cathode Ray Tube) and displays commands inputfrom the operation unit 23, data and so forth in response to displaycommand signals input from the control unit 21.

The communication unit 25 includes a wireless LAN adaptor and controlsdata sending/receiving to/from external apparatuses such as theradiation generation apparatus 1 and the FPD cassette 4 connected to acommunication network, such as a wireless LAN, via the access point 3.

The connector 26 is for communicate/connect with the FPD cassette 4 viaa not-shown cable.

Back to FIG. 1, the access point 3 relays, for example, communicationsbetween the radiation generation apparatus 1 and the console 2 andcommunications between the console 2 and the FPD cassette 4.

The FPD cassette 4 is a portable dynamic radiation detector. The FPDcassette 4 is constituted of radiation detection elements arranged atpredetermined points on a substrate, such as a glass substrate, in amatrix (two-dimensionally). The radiation detection elements detectradiation (i.e., intensity of radiation) emitted from the radiationsource 11 and at least passing through a subject H, convert the detectedradiation into electric signals, and accumulate the electric signalstherein. The radiation detection elements are connected to switchingelements such as TFTs (Thin Film Transistors), and the switchingelements control accumulation/reading of the electric signals in/fromthe radiation detection elements, whereby image data (frame images) areobtained. There are an indirect conversion type FPD which convertsradiation into electric signals with a photoelectric conversionelement(s) via a scintillator(s) and a direct conversion type FPD whichdirectly converts radiation into electric signals. Either of them can beused here.

The FPD cassette 4 includes: a reading control unit which controls theswitching elements to accumulate and read the electric signals; and acommunication unit which communicates/connects with the console 2 viathe access point 3 (both not shown). The image reading conditions suchas a frame rate, the number of frame images taken by each imaging and animage size (matrix size) are set by the console 2 through thecommunication unit. The reading control unit controls the switchingelements to accumulate/read the electric signals in/from the radiationdetection elements based on the set image reading conditions. The FPDcassette 4 has a connector to communicate/connect with the console 2 viaa not-shown cable.

The FPD cassette 4 may be carried by a photographer such as aradiologist. However, the FPD cassette 4 is relatively heavy and may bebroken or damaged when dropped. Therefore, the FPD cassette 4 isconfigured to be conveyed by being inserted into a cassette pocket 61provided on the visiting cart.

(Actions of Dynamic Analysis System 100)

Next, actions of the dynamic analysis system 100 are described.

First, an imaging action is described.

FIG. 3 shows the flow of the imaging control process performed by theconsole 2 in response to operations thereon by a photographer such as aradiologist. The imaging control process is performed by the controlunit 21 in cooperation with the imaging control process program storedin the storage unit 22.

First, a radiologist or the like operates the operation unit 23 of theconsole 2 so as to input imaging order information which includespatient information (name, height, weight, build, age, sex, etc. of apatient) on an imaging target (i.e., a subject H), an examination targetsite and an analysis target (i.e., a characteristic amount to calculate)(Step S1).

Next, the control unit 21 reads the radiation emission conditions fromthe storage unit 22 so as to set them in the radiation emission controlunit 12 through the communication unit 25, and also reads the imagereading conditions from the storage unit 22 so as to set them in thereading control unit of the FPD cassette 4 through the communicationunit 25 (Step S2).

Next, the control unit 21 waits for a radiation emission command to beinput from the exposure switch 13 (Step S3). During this period of time,the radiologist performs positioning of the patient. More specifically,the radiologist positions the subject H such that the front (or back orside) chest of the subject H faces the radiation source 11. In addition,the radiologist positions the FPD cassette 4 on the side of the subjectH opposite to the side which faces the radiation source 11 in such a wayas to face the radiation source 11 via the subject H. When completes thepositioning, the radiologist operates the exposure switch 13 so as toinput a radiation emission command.

When receives the radiation emission command input from the exposureswitch 13 (Step S3; YES), the control unit 21 outputs an imaging startcommand to the radiation emission control unit 12 and to the FPDcassette 4 to start dynamic imaging (Step S4). That is, the radiationsource 11 emits radiation at pulse intervals set in the radiationemission control unit 12 in the case of pulse emission or continuouslyemits radiation without a break at a dose rate set in the radiationemission control unit 12 in the case of continuous emission, andaccordingly the FPD cassette 4 obtains a series of frame images.Preferably, the number of frame images taken by one dynamic imagingcovers at least one cycle of respiration.

Each time a frame image is obtained by imaging, the obtained frame imageis input from the FPD cassette 4 to the console 2 through thecommunication unit 25 and stored in the storage unit 22, the frame imagebeing correlated with a number indicating what number in the imagingorder the frame image has been taken (Step S5), and also displayed onthe display unit 24 (Step S6). The radiologist checks the positioning orthe like with the displayed dynamic image and determines whether thedynamic image obtained by dynamic imaging is suitable for diagnosis(Imaging OK) or re-imaging is necessary (Imaging NG). Alternatively,after dynamic imaging finishes, automatically or in response to anoperation through the operation unit 23, all the frame images obtainedby dynamic imaging may be read from the storage unit 22 and successivelydisplayed on the display unit 24 by being switched (as a video) ordisplayed on the display unit 24 by being arranged next to one another.Then, the radiologist determines whether the dynamic image obtained bydynamic imaging is suitable for diagnosis (Imaging OK) or re-imaging isnecessary (Imaging NG). When determines either one of the “Imaging OK”and “Imaging NG”, the radiologist operates the operation unit 23 so asto input the determination result.

When the determination result “Imaging OK” is input by the radiologistmaking a predetermined operation through the operation unit 23 (Step S7;YES), the control unit 21 attaches, to the respective frame imagesobtained by dynamic imaging and stored in the storage unit 22 (e.g.,writes, in the header region of the image data in DICOM format),supplementary information which includes an ID to identify the dynamicimage, the patient information, the examination target site, theanalysis target, the radiation emission conditions, the image readingconditions, and the respective numbers indicating what number in theimaging order the respective frame images have been taken (Step S8), andthen the imaging control process ends. On the other hand, when thedetermination result “Imaging NG” is input by the radiologist making apredetermined operation through the operation unit 23 (Step S7; NO), thecontrol unit 21 deletes the frame images from the storage unit 22 (StepS9), and then the imaging control process ends.

Next, the dynamic analysis process performed on the dynamic image, whichis stored in the storage unit 22 by the above imaging control process,is described.

During or after surgeries, patients are often connected to medicaltubes, such as central venous catheters and drainage tubes.Conventionally, when dynamic X-ray imaging is performed to image thechests of these patients who are subjects and dynamic analysis isperformed on the obtained dynamic images, movements of the medical tubesaccompanying body movement, pulsation and/or respiration of the patientsbecome artifacts in the analysis results.

Hence, in the dynamic analysis process of this embodiment, the controlunit 21 performs, before dynamic analysis, a product attenuation processon the dynamic image so as to attenuate an image signal component(s) ofa product(s) such as a metical tube(s), and then performs dynamicanalysis on the obtained dynamic image.

FIG. 4 shows the flow of the dynamic analysis process performed by theconsole 2. The dynamic analysis process is performed by the control unit21 in cooperation with the program stored in the storage unit 22.

First, the control unit 21 preforms the product attenuation process onthe respective frame images (Step S11).

FIG. 5 shows the flow of the product attenuation process performed atStep S11. The product attenuation process is performed by the controlunit 21 in cooperation with the program stored in the storage unit 22.

In the product attenuation process, first, the control unit 21 extractsthe lung field region from the respective frame images (Step S111).

As a method for extracting the lung field region, any method can beused. For example, a threshold value is obtained from a histogram ofsignal values (density values) of pixels of the frame images bydiscriminant analysis, and a region having a higher signal value(s) thanthe threshold value is extracted as a lung field region candidate, andthen edge detection is performed on around the border of the extractedlung field region candidate, and points where the edge is the maximumare extracted along the border in a small region around the border,whereby the border of the lung field region is extracted.

Next, the control unit 21 performs a product recognition process on thelung field region extracted from the respective frame images so as torecognize a product region(s) (Step S112).

Medical tubes are representative of products placed in the bodies ofpatients. Hence, hereinafter, a case is described where the region of athin tube-shaped object is recognized as a product region. However,products are not limited thereto.

At Step S112, in order to recognize the product region, the control unit21 first generates an edge-enhanced image of a thin tube-shaped object(product), and then performs edge detection on the edge-enhanced image.

More specifically, the control unit 21 first performs a sharpeningprocess such as a spatial frequency enhancement process on the lungfield region extracted from the respective frame images so as togenerate an image enhancing the edge of the product (i.e., theedge-enhanced image).

At the time, a GUI (Graphical User Interface) for a user to input thesize (thickness/diameter) of the used product from the operation unit 23may be displayed on the display unit 24, and a filter to enhance aspatial frequency for the size (thickness/diameter) of the product inputin response to an operation through the operation unit 23 is used toenhance the edge of the product having the input size(thickness/diameter). This can improve accuracy of product recognition.

Alternatively, a GUI for a user to input the type of the product, whichis inserted into the patient, from the operation unit 23 may bedisplayed on the display unit 24 so as to enhance the edge of theproduct according to the input type of the product. For example, if theproduct is a central venous catheter, generally used for adults is acatheter having a thickness (diameter) of about 1 to 3 mm, if theproduct is a chest drainage tube, generally used for adults is a tubehaving a thickness (diameter) of about 4 to 15 mm, and if the product isa tracheal tube although it is not often captured in the lung fieldregion, generally used for adults is a tube having a thickness(diameter) of about 6 to 9 mm. Hence, for example, if the input type ofthe product is the central venous catheter for adults, a filter toenhance a spatial frequency of about 1 to 3 mm is used for edgeenhancement. More specifically, in order to enhance two edges formed bythe lateral face sides of the tube (both ends in the diameterdirection), it is preferable to set a size D*c (here, 0<c<1) smallerthan the thickness (diameter) D of the tube as a spatial frequency to beenhanced by a filter. This can improve accuracy of product recognition.For edge enhancement, a Sobel filter or a Canny filter may also be used.

Alternatively, movement of the product between the frame images of thedynamic image caused by movement of the subject H may be utilized toenhance the edge of the product. That is, a difference value(s) betweenthe frame images of the dynamic image adjacent to one another(hereinafter may be referred to as “inter-frame difference values”) maybe calculated to enhance the edge of the product.

After generated, the edge-enhanced image is binarized with apredetermined threshold value so as to generate an edge-detected imagein which, for example, “1” is assigned to edge candidate points (pixels)of the product and “0” is assigned to the other points (pixels).Preferably, an expansion process is performed on the edge-detected imageso as to connect the edge candidate points close to one another, therebyform a mass thereof. In the expansion process, preferably, aparameter(s) suitable for the size of the product is used. For example,if the product is a tube, the edge candidate points within apredetermined distance corresponding to the thickness/diameter of thetube are connected so as to unite the edge candidate points of two linesformed by the lateral face sides of the tube (both ends in the diameterdirection) into a mass. Thereby, the edge candidate points can beexpressed as one line. Further, in order to easily detect the shape ofthe line, which is formed of the connected edge coordinate points, bythe below-described contour detection process, preferably, a thinningprocess is performed on the edge-detected image, which is formed of theedge candidate points connected by the expansion process, so as toexpress the line as a line of edge candidate points having a width ofone point (pixel). Next, the contour detection process is performed onthe edge-detected image so as to detect the edge candidate points as astraight line(s) and a curve(s) by generalized Hankel Fouriertransformation with a straight line/arc/broken ellipse as a model,polynomial approximation with a spline interpolation method, a dynamiccontour method, or the like. In order to simplify the shape of the lineto detect as well as in order to reduce the degree of the curve(s),preferably, first, the edge-detected image is divided into several toseveral ten blocks having the same size, next, the contour detectionprocess is performed on the respective blocks, and then the blocks arecombined to form an image having the original size. Then, a regionenclosed by the contours (straight line(s) and curve(s)) detected by thecontour detection process is recognized as the product region. When theproduct is a tube, preferably, the expansion process is performed on thecontour-detected image such that the width formed of the detectedcontours corresponds to the thickness/diameter of the tube, and theexpanded contour(s) is recognized as the product region. When theproduct is a tube, alternatively, without the contour detection process,the expansion process may be performed on the thinned edge-detectedimage such that the width formed of the thinned edge candidate pointscorresponds to the thickness/diameter of the tube, and the expanded edgecandidate points are regarded as the product region. Omission of thecontour detection process can shorten the processing time forrecognition of the product region.

Bone regions of ribs, collarbone and so forth in frame images are easilymistakable for product regions. Hence, it is possible to, before theabove-described recognition of the product region, recognize boneregion(s) of ribs, collarbone and so forth from the respective frameimages, attenuate the image signal component of the recognized boneregion, and recognize the product region from the region except the boneregion in the respective frame images.

Bone regions can be recognized, for example, by template matching withprepared rib template, collarbone template and so forth or curve fittingafter edge detection as described in U.S. Patent Application PublicationNO. 2014/0079309. Further, whether the recognized bone regions arecorrect may be carefully inspected with preliminary knowledge about thebone structures of ribs, collarbone and so forth, such as theirpositions, shapes, sizes, density gradients and directions, and when itis determined that there is an excessively extracted portion(s), theportion can be removed from the bone region(s).

The image signal component of the bone region can be attenuated, as withSteps S113 and S114 described below, by creating a density profile ofthe bone region for each frame image and subtracting, from the frameimage, the value(s) of the density profile from which noise or the likehas been removed.

Alternatively, it is possible to, after the above-described recognitionof the product region, recognize a bone region(s) from the respectiveframe images, and recognize the region except the recognized bone regionin the recognized product region as the final product region.

Next, the control unit 21 creates, with respect to each of the frameimages, a density profile of the recognized product region (Step S113).More specifically, the control unit 21 creates, with respect to each ofthe frame images, a density profile(s) of the recognized productregion(s) in a cross-sectional direction. For example, in the case wherethe product is a tube, a density profile in a line which isperpendicular to a running direction of the tube is the density profilein the cross-sectional direction. The density profile of the productregion in the cross-sectional direction is, as shown in FIG. 6, createdby plotting density change in the product region in the cross-sectionaldirection with the horizontal axis showing the position in thecross-sectional direction and the vertical axis showing the signal value(pixel value).

Preferably, the density profile of the product region in thecross-sectional direction created for a frame image is compared with thedensity profiles created for frame images before and after the frameimage so as to correct the value(s) to subtract to be approximately thesame as those for the frame images before and after the frame image.

For example, with respect to each pixel of a frame image of interest,the value of the density profile of the product region in thecross-sectional direction in the frame image of interest is comparedwith (i) the representative value (e.g., the median or the average)obtained from the density profiles of the product region in thecross-sectional direction in the frame images before and after the frameimage of interest or (ii) the value of the density profile of theproduct region in the cross-sectional direction in its adjacent frameimage (frame image immediately before or after the frame image ofinterest), and if difference therebetween is equal to or more than apredetermined threshold value, the value is replaced by the comparedvalue (representative value) for example, whereby the density profile ofthe frame image of interest is corrected. Alternatively, as shown inFIG. 6, agreement of waveforms at a position may be evaluated byobtaining correlation or the like at the position (e.g., a crosscorrelation coefficient) between the waveform showing the densityprofile of the product region in the cross-sectional direction in aframe image of interest and (i) the waveform obtained from therepresentative value (e.g., the median values) of the density profilesin the frame images before and after the frame image of interest or (ii)the waveform showing the density profile in its adjacent frame image(frame image immediately before or after the frame image of interest),and if the agreement (correlation value) is lower than a predeterminedthreshold value, the waveform is replaced by the compared waveform forexample, whereby the density profile of the frame image of interest inthe cross-sectional direction is corrected at the position and hencecorrected overall.

Thereby, at Step S114, the value(s) of the density profile to subtractfrom a frame image is approximately the same as those to subtract fromthe frame images before and after the frame image. This can prevent aproduct-attenuated frame image from being greatly different from theproduct-attenuated frame images before and after the product-attenuatedframe image. Hence, for example, when a difference value betweencorresponding pixels or between corresponding regions of different frameimages, such as frame images adjacent to one another, is calculated, thedifference value is not affected by variation in the product attenuationprocess performed on the respective frame images. Consequently, onlychange in the lung field caused by respiration or bloodstream can beextracted with higher accuracy.

Next, the control unit 21 generates images with the image signalcomponent of the product attenuated (i.e., the product-attenuated frameimages) by applying a low-pass filter to the created density profiles soas to remove a high spatial frequency component such as noise from thedensity profiles and subtracting, from the respective frame images, thevalues of their respective density profiles from which noise or the likehas been removed (Step S114).

If the product attached to the patient is a thin product having athickness (diameter) of less than 1 mm, such as a central venouscatheter for children, Steps S112 to S114 may be omitted because theproduct hardly affects the analysis result. Instead, smoothing may beperformed to attenuate the image signal component of the product with asmoothing filter for a block size of each side several times thediameter of the product.

When the product attenuation process ends, the dynamic analysis processreturns to Step S12 in FIG. 4, so that the control unit 21 displays thedynamic image after the product attenuation process on the display unit24 (Step S12). As displaying the dynamic image, the frame images afterthe product attenuation process may be displayed on the display unit 24by being switched in order (as a video), or displayed on the displayunit 24 by being arranged next to one another.

Displaying the dynamic image after the product attenuation processallows a user to check what images are input for dynamic analysis. AtStep S12, preferably, the dynamic image after the product attenuationprocess and the dynamic image before the product attenuation process aredisplayed (i) in a switchable manner in response to operations throughthe operation unit 23 or (ii) next to each other. Displaying the dynamicimage after the product attenuation process and the dynamic image beforethe product attenuation process to be comparable with each other allowsa user to check and determine how the dynamic image has been changed bythe product attenuation process and if the dynamic image after theproduct attenuation process is suitable for dynamic analysis.

Next, the control unit 21 performs dynamic analysis of the chest on thedynamic image after the product attenuation process (Step S13).

The dynamic analysis of the chest includes an analysis of calculating acharacteristic amount indicating a local motion (movement) of the lungfield and an analysis of calculating a characteristic amount indicatinga motion of the entire lung field, and also includes an analysistargeted at the ventilation function and an analysis targeted at thebloodstream function.

There are several ways of the analysis of calculating the characteristicamount indicating local signal change in ventilation in the lung field,and one of these is calculation of images showing difference betweenframe images (hereinafter “inter-frame difference images”). Theinter-frame difference images on ventilation can be calculated byperforming the following processes on the frame images.

Binning Process→Low-pass Filter Process in Time LineDirection→Inter-frame Difference Process→Noise Removal Process

The binning process is a process of, in each frame image, dividing theimage region into small regions each composed of a pixel block having apredetermined size, and with respect to each small region, calculatingthe representative value such as the average (averaging) of signalvalues of pixels composing the small region. The representative value isnot limited to the average and hence may be the median or the mode.Preferably, the size of the pixel block is suitable for a site to beanalyzed and/or a characteristic amount calculated by the analysis forimprovement of accuracy of analysis. Setting the size of the pixel blockat an integral multiple of a gap (distance) between ribs can make theproportion of ribs present in the pixel block approximately the sameeven if the ribs are moved by respiration, and therefore can reducedensity change in the pixel block caused by movement of the ribs byrespiration, and accordingly can improve accuracy of analysis.

The low-pass filter process in the time line direction is a process ofextracting temporal change in the signal value in ventilation; forexample, filtering at a cutoff frequency of 0.5 Hz.

The inter-frame difference process is a process of correlating smallregions of a series of frame images at the same pixel (regions outputfrom the same detection element in the FPD cassette 4) with one another,and with respect to each small region in the frame images, calculatinginter-frame difference values, thereby generating inter-frame differenceimages.

In the case where a still image of inter-frame difference images isgenerated, density change in the entire lung field region or positionalchange of the diaphragm is analyzed so as to calculate an inhalationperiod and an exhalation period in a series of frame images, and, withrespect to each small region in the frame images, absolute values ofpositive inter-frame difference values are added up as to the inhalationperiod, and absolute values of negative inter-frame difference valuesare added up as to the exhalation period, whereby a still image ofinter-frame difference images is generated.

At an abnormal part in ventilation, the inter-frame difference value issmall. Hence, a part locally abnormal in ventilation can be identifiedby outputting the inter-frame difference images.

There are several ways of the analysis of calculating the characteristicamount indicating local signal change in bloodstream in the lung field,and one of these is calculation of inter-frame difference images. Theinter-frame difference images on bloodstream can be calculated byperforming the following processes on the frame images.

Binning Process→High-pass Filter Process in Time LineDirection→Inter-frame Difference Process→Noise Removal Process

The high-pass filter process in the time line direction is a process ofextracting temporal change in the signal value in bloodstream; forexample, filtering at a cutoff frequency of 0.7 Hz. The other processesare the same as those described above for the inter-frame differenceimages on ventilation.

At an abnormal part in bloodstream, the inter-frame difference value issmall. Hence, a part locally abnormal in bloodstream can be identifiedby outputting this inter-frame difference images.

The analysis result is correlated with the patient information and theframe images, based on which the analysis is made, and stored in thestorage unit 22.

Next, the control unit 21 displays the analysis result, obtained at StepS13, on the display unit 24 (Step S14), and then the dynamic analysisprocess ends.

For example, in the case where the inter-frame difference images areobtained as the analysis result, the small regions in the inter-framedifference images are shown in brightness or color according to theirinter-frame difference values, and the inter-frame difference images aredisplayed on the display unit 24 as a video or by being arranged next toone another. Alternatively, a still image of inter-frame differenceimages may be generated. Then, the small regions in the still image areshown in brightness or color according to their inter-frame differencevalues, and the still image is displayed on the display unit 24.

Further, the analysis result such as the image(s) in which theinter-frame difference values are shown in color and the dynamic imagebefore the analysis may be displayed on the display unit 24 by beingarranged next to one another, displayed at the same position on thedisplay unit 24 switchably at proper timing, or displayed on the displayunit 24 by being superimposed with different transmittances. This kindof display makes it easy to compare the analysis result with the dynamicimage before the analysis, and accordingly makes it easy to understand,for example, what structure's movement in the dynamic image before theanalysis is the factor in generating the local value in the analysisresult such as the inter-frame difference images, and enables moreaccurate understanding of the state of the diseased site.

Further, the inter-frame difference images on ventilation and theinter-frame difference images on bloodstream may be displayed on thedisplay unit 24 by being arranged next to one another, displayed at thesame position on the display unit 24 switchably at proper timing, ordisplayed on the display unit by being superimposed with differenttransmittances. This kind of display makes it easy to compare anabnormal part in ventilation with an abnormal part in bloodstream, andaccordingly enables more accurate understanding of the state of thediseased site.

Further, the result of CAD (Computer-Aided Diagnosis), which is used forcancer diagnosis support or the like, and the analysis result such asthe image(s) in which the inter-frame difference values are shown incolor may be displayed on the display unit 24 by being arranged next toone another, displayed at the same position on the display unit 24switchably at proper timing, or displayed on the display unit 24 bybeing superimposed with different transmittances. This kind of displaymakes it easy to compare the CAD result in which, for example, region(s)resembling a tuber or a tumor shadow in the lung field is marked withthe analysis result such as the image(s) in which the inter-framedifference values are shown in color, and accordingly enables moreaccurate understanding of the state of the diseased site based ondetermination of whether the marked region in the CAD result agrees withthe local value in the analysis result such as the image(s) in which theinter-frame difference values are shown in color.

There is another way of the analysis of calculating the characteristicamount indicating local signal change in ventilation or bloodstream inthe lung field, which is described in Japanese Patent ApplicationPublication No. 2010-268979. It is an analysis of calculating, withrespect to each of small regions into which the lung field region isdivided, phase delay time of (i) temporal change in the pixel signalvalue to (iia) temporal change (reference temporal change) in the indexvalue indicating respiration, such as the position (up and down) of thediaphragm, in the case of ventilation or (iib) temporal change(reference temporal change) in the index value indicating pulsation ofthe heart, such as a signal value at the position of the cardiac wall orin the heart region, in the case of bloodstream, so as to calculate,with respect to which region in the lung field region, how much temporalchange in the pixel signal value delays. This calculation result may bedisplayed on the display unit 24.

There is also another way thereof. It is an analysis of calculating,with respect to each of small regions into which the lung field regionis divided, a cross correlation coefficient between (i) the waveformshowing temporal change in the pixel signal value and (iia) the waveform(reference waveform) showing temporal change in the index valueindicating respiration, such as the position (up and down) of thediaphragm, in the case of ventilation or (iib) the waveform (referencewaveform) showing temporal change in the index value indicatingpulsation of the heart, such as a signal value at the position of thecardiac wall or in the heart region, in the case of bloodstream, so asto calculate if a correlation exists therebetween. This calculationresult may be displayed on the display unit 24.

Based on the above-described phase delay time or cross correlationcoefficient, for example, a region where the phase delay time is about ahalf of a cycle of respiration or pulsation and the phase is almostinversed or a region where the cross correlation coefficient is smallerthan a predetermined value may be recognized as a region where change inthe signal value occurs by movement of a structure(s) such as ribs,namely, a bone region, and as described above, the image signalcomponent of the bone region may be attenuated by creating a densityprofile of the bone region for each frame image and subtracting, fromthe frame image, the value(s) of the density profile from which noise orthe like has been removed.

Further, about a subject H who is considered to undergo a surgery suchas pneumonectomy, it is possible to: in the analysis result displayed onthe display unit 24, such as the image(s) in which the inter-framedifference values are shown in color, select a region in the lung fieldregion, for example, a pneumonectomy region corresponding to apneumonectomy range in the lung field, by a user operating the operationunit 23 or the like; calculate, as a characteristic amount L ofventilation or bloodstream in a region except the selected region fromthe entire lung field region, an integrated value of inter-framedifference values of the region except the selected region from theentire lung field region, for example; calculate, as a characteristicamount E of ventilation or bloodstream in the entire lung field region,an integrated value of inter-frame difference values of the entire lungfield region, for example; calculate a ratio of these characteristicamounts L and E by dividing the characteristic amount L by thecharacteristic amount E; and display this result on the display unit 24as the analysis result. By selecting the pneumonectomy region as theabove-described region to select, the characteristic amount L can beregarded as the amount of ventilation or bloodstream afterpneumonectomy, and the characteristic amount E can be regarded as theamount of ventilation or bloodstream before pneumonectomy. Hence, thecalculated ratio of the characteristic amounts L and E can be regardedas a ratio of the amount of ventilation or bloodstream afterpneumonectomy to the amount of ventilation or bloodstream beforepneumonectomy, namely, a rate indicating how much the amount ofventilation or bloodstream changes by pneumonectomy. This allows a user,before pneumonectomy, to quantitatively estimate the state afterpneumonectomy.

Further, the console 2 may be configured to receive a measurementresult(s) of a different examination(s) on the subject H input throughthe operation unit 23 or the communication unit 25, calculate a valueobtained by multiplying the received measurement result of the differentexamination on the subject H by the calculated ratio of thecharacteristic amounts L and E, and display the calculated value on thedisplay unit 24 as the analysis result. For example, as theabove-described region to select, the pneumonectomy region is selected,and as the measurement result of the different examination on thesubject H, the result of spirometry before pneumonectomy is input,whereby the value obtained by multiplying the measurement result of thedifferent examination on the subject H by the calculated ratio of thecharacteristic amounts L and E can be regarded as an estimation value ofspirometry after pneumonectomy. This allows a user, beforepneumonectomy, to estimate the result of spirometry after pneumonectomyas the state after pneumonectomy, and based on this result, the user canappropriately determine whether to perform pneumonectomy on the subjectH to surgically remove the selected region.

Preferably, at Step S13, dynamic analysis is performed not only on thedynamic image after the product attenuation process but also on thedynamic image before the product attenuation process, and at Step S14,the analysis result of the dynamic image after the product attenuationprocess and the analysis result of the dynamic image before the productattenuation process are displayed (i) in a switchable manner in responseto operations through the operation unit 23 or (ii) next to each other.Displaying the analysis result of the dynamic image after the productattenuation process and the analysis result of the dynamic image beforethe product attenuation process to be comparable with each other allowsa user to check and determine how the analysis result of the dynamicimage has been changed by the product attenuation process and if theanalysis result of the dynamic image after the product attenuationprocess is appropriate.

In the above, the imaging order information is input into the console 2by a radiologist. However, the imaging order information may be inputinto the console 2 from a terminal such as an RIS (Radiology InformationSystem) connected via a cable/wireless network.

Further, when the imaging order information is input into the console 2,preferably, all or some of frame images of previously taken dynamicimage(s) of the patient, who is the imaging target, and the radiationemission conditions and the image reading conditions attached to thedynamic image(s) are (i) read from the console 2 or an image storageserver such as a PACS (Picture Archiving and Communication System)connected to the console 2 via a cable/wireless network and (ii)displayed on the display unit 24. Displaying, on the console 2, all orsome of the frame images of the previously taken dynamic image(s) of thepatient, who is the imaging target, and the radiation emissionconditions and the image reading conditions attached to the dynamicimage(s) makes it easy to image the patient under the same positioning,posture, radiation emission conditions and image reading conditions asthose in the previous imaging, and hence serves for obtaining a dynamicimage which is more easily comparable with the previously taken dynamicimage(s). Then, in order to make previously taken dynamic images readilyreferable, preferably, the console 2 stores therein particular frameimages of dynamic images or reversibly/irreversibly compressed images ofthe whole or parts of dynamic images for a long period of time.

Further, in the case of dynamic imaging without a grid for removal ofscattered rays, preferably, before the product attenuation process, ascattered ray removal process to estimate scattered ray components aboutframe images and remove the scattered ray components from the respectiveframe images is performed. This can improve contrast in the dynamicimage and improve accuracy of the product recognition process in theproduct attenuation process.

Further, there is a case where the amount of radiation emitted(hereinafter “radiation emission amount”) from the radiation generationapparatus 1 for each frame image changes during dynamic imaging, andthis temporal change in the radiation emission amount may cause errorsin the analysis result. Hence, before the product attenuation process,preferably, a radiation-emission-amount temporal-change correctionprocess is performed on the respective frame images so as to cancel thetemporal change in the radiation emission amount per frame image. Thiscorrection process may be performed by the console 2 employing a methodof obtaining information on the radiation emission amount for each frameimage from the radiation generation apparatus 1 and dividing the pixelvalue of each frame image by a value proportional to the radiationemission amount for the frame image. Alternatively, the correctionprocess may be performed by recognizing a no-notion region, such as adirectly irradiated region or a region where a subject H is captured butapproximately still, from the respective frame images and performing thecorrection process according to the pixel value of the recognizedno-motion region. This can eliminates influence of the temporal changein the radiation emission amount on the characteristic amount related tothe ventilation function or the bloodstream function, and accordinglycan improve the diagnostic accuracy based on the analysis result of thedynamic image.

In order that this correction process works properly, preferably, eachtime a frame image is obtained during dynamic imaging, or immediatelyafter dynamic imaging, the control unit 21 of the console 2 (i)determines whether the no-motion region, such as a directly irradiatedregion or a region where a subject H is captured but approximatelystill, is contained in the frame image, and (ii) when determines thatthe no-motion region is not contained therein, displays an alarm messageon the display unit 24 so as to urge a user to perform re-imaging or thelike.

Further, the console 2 may determine whether alignment of the FPDcassette 4 with the radiation source 11 and positioning of a subject Hare appropriate and also determine a parameter(s) for image processingto display the dynamic image before analysis, by still image shootingfor positioning check (scout shooting) performed immediately beforedynamic imaging starts or by analysis of one to several frame imagestaken immediately after dynamic imaging starts. If the frame image(s)taken immediately after dynamic imaging starts are analyzed, preferably,each time a frame image is obtained during dynamic imaging, the frameimage is analyzed in almost real time. Whether alignment of the FPDcassette 4 with the radiation source 11 and positioning of a subject Hare appropriate is determined as follows: in the case of dynamic imagingof the chest of a subject H, the control unit 21 performs imageprocessing and thereby first recognizes a through region which isdirectly irradiated with radiation (i.e., the directly irradiatedregion) and a subject region, next recognizes the lung field region andthe mediastinum region from the subject region, and further recognizes,from the mediastinum region, a spinous process(es), which is present inthe vertically arranged vertebrae, and pediculus arcus vertebrae,between which the spinous process is interposed; and then automaticallyperforms measurement to determine whether the spinous process is locatedat the center of the recognized pediculus arcus vertebrae and therebydetermines whether the spinous process is in the middle of the pediculusarcus vertebrae. When it is determined that the spinous process is notin the middle of the pediculus arcus vertebrae, it is assumed thatradiation is emitted not perpendicularly but obliquely to the surface ofthe FPD cassette 4, and accordingly a message to change alignment of theFPD cassette 4 with the radiation source 11 is displayed on the displayunit 24. At the time, it is far preferable that the vertebra where thespinous process and the pediculus arcus vertebrae are recognized isenlargedly displayed on the display unit 24 because this makes it easyfor a user to grasp how much the radiation source 11 should be moved.

Further, the console 2 or the FPD cassette 4 may recognize the lungfield region by still image shooting for positioning check (scoutshooting) performed immediately before dynamic imaging starts or byanalysis of one to several frame images taken immediately after dynamicimaging starts, and determine a region of “circumscribed quadrilateralof the recognized lung field region×α (α>1)” as a target region, and theFPD cassette 4 may read only the determined target region in obtainingthe following frame images or may read the entire region but transferonly the determined target region in the read entire region to theconsole 2. The target region may be determined/set to contain apredetermined area (size) of the directly irradiated regioncorresponding to a region of the FPD cassette 4 directly irradiated withradiation emitted from the radiation source 11. Limiting the region readby the FPD cassette 4 or the region to transfer from the FPD cassette 4to the console 2 to a certain region can reduce the amount ofelectricity consumed by the reading or the transfer and also can reducethe storage capacity of a storage unit of the FPD cassette 4 and/or thestorage capacity of the storage unit 22 consumed by storing image data.

Further, in order to prevent blurring caused by movements (motionartifacts) of the radiation source 11 and a subject H, preferably, theradiation generation apparatus 1 emits radiation by pulse emission fromthe radiation source 11. If the radiation generation apparatus 1 onlyhas a function of continuously emitting radiation without a break(continuous emission) from the radiation source 11, the radiationgeneration apparatus 1 may be provided, at a radiation exit of theradiation source 11, with a not-shown aperture stop part to reduce theirradiated field of radiation. The aperture stop part has a shutter tocompletely block output of radiation, and drives opening/closing of theshutter at desired timing, and thereby changes continuous emission topulse emission. Consequently, the radiation generation apparatus 1 canemit radiation by pulse emission. Preferably, the aperture stop part andthe FPD cassette 4 are configured to be in sync such that timing atwhich the shutter of the aperture stop part is opened to emit pulsedradiation is within the accumulation time of the FPD cassette 4.Further, the aperture stop part having the shutter opening/closingmechanism is, preferably, configured to be externally attachable to theradiation source 11. Hence, even if a radiation generation apparatusinstalled in a facility is for still image shooting and can emitradiation only for a short time but can realize continuous emission byemitting radiation (i.e., single radiation) longer than usual, theradiation generation apparatus can realize pulse emission at low costwithout being entirely replaced, with the attachable aperture stop partbeing externally attached to the radiation source 11 thereof. Manyradiation generation apparatuses for still image shooting areapparatuses having a minimum settable tube current of 10 mA or 20 mA,but in the case of dynamic imaging, in order to reduce the totalexposure dose of a subject, a dose rate of radiation emitted to asubject should be kept low, for example, at a dose rate of radiationemitted when the tube current is set at about 0.5 to 3 mA. Then, theaperture stop part is externally attached to the radiation source 11 ofsuch a radiation generation apparatus for still image shooting, andcyclically closes the shutter to block the single radiation, which isemitted from the radiation source 11 longer than usual, whereby pulseemission is realized. Accordingly, the dose rate of radiation emitted toa subject from the radiation generation apparatus for still imageshooting can be reduced to a dose rate suitable for dynamic imaging, andthe total exposure dose of the subject can be kept low. In order tofurther reduce the dose rate, the aperture stop part may have astructure to attach an added filter to the radiation exit of theaperture stop part.

Further, the visiting or portable radiation generation apparatus 1 ismovable and compact and therefore often has a long rising time for thetube voltage to rise to around a set value immediately after radiationemission starts and a long falling time for the tube voltage to fall toalmost 0 immediately after radiation emission ends. During these periodsof time that the tube voltage rises to around the set value and the tubevoltage falls to almost 0, radiation having a low tube voltage isemitted, and hence a frame image(s) meeting a desired image quality foranalysis cannot be generated, and the exposure dose of a subject Hincreases for nothing. Hence, preferably, the aperture stop part has afunction of blocking radiation by closing the shutter with the shutteropening/closing mechanism when the tube voltage is lower than a desiredvalue, such as immediately after radiation emission starts orimmediately after radiation emission ends. This allows only radiationhaving a tube voltage at which frame images suitable for analysis aregenerated to be emitted to a subject H, and hence can reduce oreliminate unnecessary exposure of the subject H to radiation.Alternatively, control may be made not to perform reading of the FPDcassette 4, storage of image data into the storage unit of the FPDcassette 4 and/or sending of image data from the FPD cassette 4 to theconsole 2 through the communication unit 25 while a predetermined numberof frame images are taken immediately after radiation emission starts orfor a predetermined period of time immediately after radiation emissionstarts. This can reduce power consumption of the FPD cassette 4 duringemission of radiation having a low tube voltage at which frame imagesunsuitable for analysis are generated, and if the FPD cassette 4 isdriven by a battery, can reduce consumption of the battery too. Further,because frame images unsuitable for analysis are not stored in thestorage unit of the FPD cassette 4, the storage capacity of the storageunit of the FPD cassette 4 can be effectively used.

As described above, immediately after radiation emission starts/ends,the tube voltage is lower than a desired value, and radiation suitablefor analysis is not emitted from the radiation source 11, so that theaperture stop part closes the shutter with the shutter opening/closingmechanism, thereby blocking radiation emitted from the radiation source11. Then, during a portion of this period of time, the FPD cassette 4may obtain one to several frame images, and these frame image(s)obtained by the FPD cassette 4 without being irradiated may be used asimage data for offset correction to remove offset values resulting fromdark current superposed on the frame images obtained by the FPD cassette4 with being irradiated. This makes it possible to obtain image data forthe offset correction at a time quite close to a period of time that theFPD cassette 4 is being irradiated, and accordingly increase accuracy ofthe offset correction to remove the offset values and obtain frameimages (i.e., a dynamic image) suitable for analysis and diagnosis.

Further, in the case of dynamic imaging of the breathing state of thechest of a subject H, respiration of the subject H may be measured witha noncontact sensor such as a microwave sensor outputting radio wavesand receiving reflected waves from the surface of the subject H, andrespiration information on the subject H may be displayed on the displayunit 24 of the console 2 in real time. Extraction of respirationinformation on a subject H with a sensor separate from the FPD cassette4 allows a user to monitor respiration of the subject H even not duringradiation emission, and allows the user, according to the respiration ofthe subject H, to determine timing of the start of radiation emission.The respiration information such as the phase of respiration obtainedwith a sensor separate from the FPD cassette 4 is preferably attached toand stored with its dynamic image or the analysis result of the dynamicimage. However, in order to separately display the image data and therespiration information, which are once combined, on a server such as aPACS or a terminal such as a viewer by transferring the combined datathereto, the server or terminal needs to have the structure of thecombined data in advance, and hence type of server or terminal which canseparately display the image data and the respiration information isvery limited. Then, the respiration information such as the phase ofrespiration may be embedded in its corresponding frame image(s) in theimage data in the form of text information as an annotation(s) or in theform of graphics as waveform data. This allows a general-purpose serveror terminal which reads the combined data to separately display theimage data and the respiration information such as the phase ofrespiration, without limiting the type of the server or terminal.

Further, the visiting or portable radiation generation apparatus 1 ismovable and compact, and hence the maximum radiation emission time isshort, so that there is a case where the radiation generation apparatus1 cannot take images of one cycle of respiration by one dynamic imaging.In such a case, for example, it is possible that respiration of thesubject H is monitored even not during radiation emission with a sensorseparate from the FPD cassette 4 as described above; the phase at theend of radiation emission in the first dynamic imaging is stored; and,in the second dynamic imaging, control is made, based on the output ofthe sensor, not to start radiation emission until respiration of thesubject H becomes the stored phase even if a user instructs start ofradiation emission, and start radiation emission at the timing whenrespiration of the subject H becomes the stored phase. If necessary, thephase at the end of radiation emission in the second dynamic imaging mayalso be stored, and in the third dynamic imaging and thereafter, theabove-described control may be made. This can make the last frame imagetaken by one dynamic imaging match the first frame image taken by thenext dynamic imaging in phase. By combining the taken dynamic images inorder, one dynamic image is generated. Thus, even if the maximumradiation emission time is short and images of one cycle of respirationcannot be taken by one dynamic imaging as described above, a dynamicimage which is substantially the same as that generated by continuouslytaking images of one cycle of respiration can be generated and analyzedwithout unnecessary exposure of a subject H to radiation.

Second Embodiment

Next, a second embodiment of the present invention is described.

The dynamic analysis system 100 of the second embodiment is, inconfiguration, the same as that of the first embodiment described withreference to FIG. 1 and FIG. 2 except that, in the second embodiment,the radiation generation apparatus 1 can emit radiation of differentenergy levels (tube voltages) and perform imaging by switching theenergy levels in order at the beginning or end of dynamic imaging,whereby k frame images for an energy subtraction process can beobtained. The console 2 can set, through the operation unit 23,radiation emission conditions for obtaining k frame images for theenergy subtraction process in addition to the radiation emissionconditions for dynamic imaging. The radiation emission conditions forobtaining k frame images for the energy subtraction process include: j(j≥2) energy levels (tube voltages) to switch; the number of times kthat imaging is performed with energy levels being switched; andswitching order of energy levels. Because imaging is performed withenergy levels being switched, preferably, the radiation generationapparatus 1 emits radiation by pulse emission from the radiation source11.

The energy subtraction process is a process to extract or attenuate astructure(s) having a predetermined linear attenuation coefficient byperforming mathematical operation on j frame images which are takencontinuously in terms of time with j energy levels being switched. Thenumber of times k that imaging is performed with j energy levels beingswitched for the energy subtraction process is equal to or more than thenumber of energy levels j.

For example, if frame images for the energy subtraction process areobtained at the beginning of dynamic imaging, and the number of energylevels is three (energy levels A, B, C), k=j may hold as described inthe following Case (1) or k≠j may hold as described in the followingCase (2).

Case (1) (k=j); A, B, C, C, C, . . . : in the first three times ofimaging in dynamic imaging, radiation of three energy levels is emittedby the energy levels being switched, whereby frame images for the energysubtraction process are obtained; and subsequently, radiation of theenergy level C is emitted for imaging multiple times, the energy level Cbeing the same as the last energy level in obtaining the frame imagesfor the energy subtraction process, whereby frame images for dynamicanalysis are obtained by imaging with the energy level C.

Case (2) (k≠j); A, B, C, A, B, B, B . . . : in the first five times ofimaging in dynamic imaging, radiation of three energy levels is emittedby the energy levels being switched, whereby frame images for the energysubtraction process are obtained; and subsequently, radiation of theenergy level B is emitted for imaging multiple times, the energy level Bbeing the same as the last energy level in obtaining the frame imagesfor the energy subtraction process, whereby frame images for dynamicanalysis are obtained by imaging with the energy level B.

That is, in the second embodiment, at Step S2 of the imaging controlprocess shown in FIG. 3, the radiation emission conditions, whichinclude the energy levels of radiation to switch, the number of timesthat imaging is performed with the energy levels being switched and theswitching order of energy levels, for the energy subtraction process,are set in the radiation generation apparatus 1. Further, at Step S4, atthe beginning or end of dynamic imaging, the radiation generationapparatus 1 switches the set j energy levels of radiation to performimaging k times, whereby a dynamic image including k (k≥j) frame imagesfor the energy subtraction process is obtained.

The console 2 performs the dynamic analysis process on the dynamic imageobtained by the imaging control process, as with the first embodiment.However, the product recognition process (Step S112) in the productattenuation process at Step S11 in the second embodiment is differentfrom that in the first embodiment. Hereinafter, the product recognitionprocess performed by the control unit 21 in the second embodiment isdescribed.

First, the control unit 21 performs the product recognition processemploying the energy subtraction process, using the first or last kframe images of the dynamic image obtained by dynamic imaging, therebyobtaining k−j+1 product-enhanced images (product-recognized images). Theproduct recognition process employing the energy subtraction process isa process to obtain images in which a product(s) is recognized by:performing mathematical operation on, among the first or last k frameimages of the dynamic image, j frame images continuous in terms of timetaken with radiation of j different energy levels; and attenuating theimage signal components of bones and soft tissue of the subject Hcaptured in the dynamic image, for example.

In order to attenuate the image signal components of both bones and softtissue of the subject H captured in the dynamic image, preferably, thenumber of energy levels j is three or more. If i types of productshaving different linear attenuation coefficients of energycharacteristics are captured in the dynamic image, preferably, thenumber of energy levels j is i+2 or more, and mathematical operationwith the following Formulae is performed on each j frame imagescontinuous in terms of time taken with radiation of j different energylevels so as to attenuate the image signal components of bones and softtissue of the subject H and product(s) having other linear attenuationcoefficient(s) of energy characteristics, whereby i product-enhancedimages in which only respective i products having respective linearattenuation coefficients of energy characteristics are enhanced areobtained.

In j frame images continuous in terms of time taken with radiation of jdifferent energy levels, when p1 to pj respectively represent signalvalues of the same pixel, pixel values Pe1 to Pei respectively enhancing(extracting) i products respectively having linear attenuationcoefficients e1 to ei of energy characteristics can be obtained bymathematical operation with the following Formulae, for example.Pe1=α11*P1+α12*P2+α13*P3+ . . . +α1jPjPe2=α21*P1+α22*P2+α23*P3+ . . . +α2jPj. . .Pei=αi1*P1+αi2*P2+αi3*P3+ . . . +αijPj   [Formulae]

(α11 to αij represent real number coefficients.)

Preferably, the mathematical operation method for j frame images ischanged (the coefficients α11 to α1j are changed) according to the typeof product; to be specific, according to i types of products havingdifferent linear attenuation coefficients of energy characteristics.Here, it is possible to display a GUI on the display unit 24 to input,from the operation unit 23, the type and/or material of product insertedinto a patient, identify the linear attenuation coefficient of energycharacteristics of the product according to the input type and/ormaterial of product, and set coefficients α11 to α1j based on theidentified linear attenuation coefficient of energy characteristics ofthe product.

A product-enhanced image obtained by adding up, with respect to eachpixel, values of the same pixel in i product-enhanced images obtainedwith the above Formulae is output as the result of the productrecognition process. Alternatively, it is possible to: binarize each ofi product-enhanced images, which are obtained with the above Formulae,with a predetermined threshold value; obtain a region showing one of thetwo values in each product-enhanced image as a product region image;composite the obtained i product region images, for example, byregarding a pixel(s) as a product region if at least one of the iproduct region images shows that the pixel(s) constitutes the productregion (i.e., OR operation); and output the result of the composition asthe result of the product recognition process. Performing the productrecognition process by using j frame images continuous in terms of timetaken with radiation of j energy levels while shifting the frame imagescan generate the results of the product recognition process of k−j+1frame images continuous in terms of time. For example, in the above Case(2) where imaging is performed with j=3 energy levels A, B, C beingswitched to be A, B, C, A, B, B, B . . . , performing the productrecognition process employing the energy subtraction process by usingk=5 frame images taken with A, B, C, A, B on each three frame imagescontinuous in terms of time taken with three different energy levels,namely, on each of groups ABC, BCA and CAB, can generate k−j+1=3product-enhanced images.

In the case of “k−j+1>1”, preferably, the results of the productrecognition process of the first or last k−j+1 images are compared withone another so as to be corrected. Further, on the product-enhancedimages obtained by the above process, the product recognition process atStep S112 in FIG. 5 described in the first embodiment or the like may beperformed to recognize the product(s). This can improve accuracy ofproduct recognition.

After obtains k−j+1 frame images in which the product is recognized bythe product recognition process employing the energy subtractionprocess, the control unit 21 performs the product recognition processemploying simple image processing on the remaining frame images on whichno product recognition process is performed yet, based on the results ofthe product recognition process of the k−j+1 frame images.

The simple product recognition process is a process to recognize aproduct region(s), for example, by: referring to the product regionrecognized in the frame image immediately before a frame imageconcerned; and searching only several pixels in the surroundings of theborder part of the product region in the frame image concerned for thespatial edge (gradient) of the product so as to extract the edge of theproduct therein. This can reduce the computation and enables high-speedprocessing as compared with the case where the complete productrecognition process is performed on all of the frame images. A methodfor extracting the spatial edge of a product with high accuracy isexemplified by a dynamical contour extraction method. This is a methodof: taking coordinates of a product region extracted in a frame imageimmediately before a frame image concerned as the initial position; andperforming contour extraction multiple times with (i) the shape of theproduct and (ii) the edge characteristics on the frame image, asevaluation functions. This can catch the contour of a product with highaccuracy. This dynamical contour extraction method can flexibly dealwith change in shape/position of a product which is a target and hencecan be used for frame images between which change is large.

For further simplification, for example, if the taken image is a dynamicimage of the chest in the breathing state, a product(s) usually moves atinhalation and exhalation in a particular direction according to thetype of the product. Hence, it may be determined whether each frameimage has been taken during inhalation or exhalation, and search for theedge of a product may be performed in a particular direction accordingto the type of the product; for example, when it is determined that aframe image has been taken during inhalation, search for the edge of aproduct is performed only in the down direction in relation to theproduct region extracted in its immediately-before frame image, whereaswhen it is determined that a frame image has been taken duringexhalation, search for the edge of a product is performed only in the updirection in relation to the product region extracted in itsimmediately-before frame image. If multiple types of products arecaptured as described above, the direction to search for the edge may bechanged according to the type of product and the timing (i.e., duringinhalation or exhalation), whereby products are extracted type by type.

Whether a frame image has been taken during inhalation or exhalation canbe determined by detection of a moving direction of the diaphragm ordensity change (increase/decrease) in the lung field region in relationto its immediately-before frame image. In the case of the movingdirection of the diaphragm, if the diaphragm moves in the downdirection, it is during inhalation, whereas if the diaphragm moves inthe up direction, it is during exhalation. In the case of the densitychange in the lung field region field, if the density increases, it isduring inhalation, whereas if the density decreases, it is duringexhalation. Because the diaphragm has a large density gradient,detection of the edge of the diaphragm makes it easy to determinewhether a frame image concerned has been taken during inhalation orexhalation. Although the lung field region can be recognized as withStep S111 by detection of the edge of the chest, even withoutrecognition of the lung field region, whether a frame image has beentaken during inhalation or exhalation can be determined by detection of,for example, the density increase/decrease in a predetermined region atthe center of the frame image.

Thus, successively processing frame images by referring to the resultsof the product recognition process of their respectiveimmediately-before frame images can simplify the product recognitionprocess performed on the frame images and increase the processing speedof the product recognition process performed thereon.

While j frame images used for one energy subtraction process are taken,body movement, respiration and/or pulsation of the subject H occur, andaccordingly the shadow of a structure captured in the respective frameimages shifts in position. Therefore, it is preferable to perform apositioning process to correct the shift in position. Further, in eachframe image of a dynamic image taken with radiation of low energy, theamount of noise is large in a region corresponding to a structure in asubject H, the structure having a low X-ray transmittance. Hence, it ispreferable to perform a noise reduction process to make noiseunnoticeable. However, the positioning process and the noise reductionprocess each take much processing time. In addition, the switching timeinterval to switch energy levels of radiation between frames has alimit, and accordingly the frame rate has a limit (upper limit).

Hence, the number of frame images used for the energy subtractionprocess is limited to k. This can increase the processing speed of theproduct recognition process performed on the entire dynamic image, canshorten a period of time for taking k frame images, performing theproduct attenuation process on the entire dynamic image and thendisplaying or inputting in the dynamic analysis process the dynamicimage after the product attenuation process, and also, by taking onlythe first or last k frame images of the dynamic image at a frame ratelower than a preferable frame rate so as to switch energy levels ofradiation, can take the remaining frame images at the preferable framerate. If the processing time and the frame rate are sufficient, theproduct recognition process employing the energy subtraction process maybe performed on all of the frame images of the dynamic image.

The processes at Step S113 and thereafter are the same as those in thefirst embodiment and therefore explanation thereof is omitted here.

As described above, according to the second embodiment, the completeproduct recognition process is performed on only some frame images andthe simple product recognition process is performed on the remainingframe images. This can reduce the computation and enables high-speedprocessing.

In the second embodiment, the product recognition process employing theenergy subtraction process is performed on some of a series of frameimages, and the simple product recognition process is performed on theremaining frame images. The simple product recognition process is aprocess to recognize a product region(s) by: referring to the productregion already recognized by the product recognition process; andsearching only several pixels in the surroundings of the border part ofthe product region for the spatial edge (gradient) of the product so asto extract the edge of the product. However, instead of the productrecognition process employing the energy subtraction process, anotherproduct recognition process, such as the product recognition processdescribed in the first embodiment, may be performed.

An image in which only soft tissue is extracted by the energysubtraction process may be used as an input image for dynamic analysisat Step S13 in FIG. 4. In the image in which only soft tissue isextracted by the energy subtraction process, the image signal componentsof products are attenuated, and hence dynamic analysis can be performedwith high accuracy. Although it depends on the type of product,difference between a product and soft tissue in liner attenuationcoefficients of energy characteristics may be not large. In such a case,in the image in which only soft tissue is extracted by the energysubtraction process, the image signal component of the product may beinsufficiently attenuated and remain. In such a case, in the completeproduct recognition process performed on only some frame images, first,as described above, product-enhanced images of respective products,which are targets of attenuation, are obtained by the energy subtractionprocess, and next, on the product-enhanced images of the respectiveproducts, the product recognition process at Step S112 in FIG. 5described in the first embodiment is performed to generate edge-enhancedimages, detect straight lines and curves, and so forth, therebyrecognizing product regions of the respective products. Based on theproduct regions of the respective products recognized by the completeproduct recognition process, the simple product recognition process isperformed on the other frame images product by product, therebyrecognizing the product regions of the respective products in therespective frame images. Then, for the respective (original) frameimages, the density profiles of the product regions of the respectiveproducts are created and the image signal components of the productregions of the respective products are attenuated, as with Steps S113and S114 in FIG. 5 described in the first embodiment, whereby animage(s) in which the image signal components of all the target productsare attenuated are obtained. Thus, an image(s) in which the image signalcomponents of target products are attenuated with high accuracy can begenerated, and the diagnostic accuracy based on analysis results ofdynamic images can be improved.

Third Embodiment

Next, a third embodiment of the present invention is described.

The dynamic analysis system 100 of the third embodiment is, inconfiguration, the same as that of the first embodiment described withreference to FIG. 1 and FIG. 2 except that, in the third embodiment, theradiation generation apparatus 1 further has a tomosynthesis imagingfunction.

That is, the radiation generation apparatus 1 has a moving mechanism tomove the radiation source 11 in a body axis direction of a subject H,and, in tomosynthesis imaging, the radiation generation apparatus 1emits radiation a predetermined number of times to the FPD cassette 4from the radiation source 11 while moving the radiation source 11, andthe FPD cassette 4 performs an image obtaining process a predeterminednumber of times and sends the obtained images to the console 2. In orderto prevent blurring caused by movements of the radiation source 11 and asubject H (motion artifacts), preferably, the radiation generationapparatus 1 emits radiation by pulse emission from the radiation source11. However, the radiation generation apparatus 1 may be configured tocontinuously emit radiation without a break (continuous emission) fromthe radiation source 11, and the FPD cassette 4 may be configured toperform the image obtaining process a predetermined number of timesduring the period of time.

The console 2 can set radiation emission conditions for tomosynthesisimaging in addition to the radiation emission conditions for dynamicimaging. Dynamic chest imaging is performed in the breathing state,whereas tomosynthesis chest imaging is performed in the breath holdingstate by imaging a chest multiple times while changing the imagingangle. Hence, before or after dynamic imaging, an operator operates theoperation unit 23 to set the conditions for tomosynthesis imaging in theconsole 2, and the imaging is performed.

A set of projection images obtained by tomosynthesis imaging issubjected to a reconstruction process performed in the console 2 by thecontrol unit 21 in cooperation with a program stored in the storage unit22 so as to generate images of multiple sections (slice surfaces)(tomographic images). These tomographic images are utilized at Step S112for the product recognition process so as to recognize a productregion(s) in the respective frame images obtained by dynamic imaging.The tomographic images obtained by tomosynthesis imaging are sectionalimages of surfaces (slices) of a subject H at a plurality of points in aradiation emission direction (z direction), the surfaces beingperpendicular to the z direction.

In the product recognition process using tomographic images obtained bytomosynthesis imaging, first, except the tomographic images of the slicesurfaces of the regions located at the body surface, which includesregions of frontal ribs, posterior ribs, collarbone and vertebrae, pixelvalues of corresponding pixels of all the (remaining) tomographic imagesare added up (integrated) so as to obtain a chest image with bonesremoved. This chest image without bones corresponds to, among a seriesof frame images obtained by dynamic imaging before or aftertomosynthesis imaging, a frame image having a breath phase the same asthe breath phase of the breath holding state in which tomosynthesisimaging is performed. On this chest image without bones, the productrecognition process described in the first embodiment is performed. Thatis, the edge enhancement by the frequency enhancement process for aproduct(s), the edge detection and the straight line/curve detection areperformed to recognize the product region(s). Because ribs have beenremoved from the chest image generated from the tomographic images,accuracy of product recognition is high as compared with the firstembodiment.

Next, on the respective frame images obtained by dynamic imaging, thesimple product recognition process described in the second embodiment isperformed based on the above-described chest image generated based onthe tomographic images, thereby recognizing the product region in therespective frame images. The size of the lung field region in the chestimage obtained from the tomographic images is the same as that in one(or more) of the frame images of the dynamic image. Hence, first, aframe image having the same lung field size as the chest image obtainedfrom the tomographic images is selected, and the simple productrecognition process is performed on the selected frame image based onthe product region recognized in the chest image, and then the simpleproduct recognition process is performed on the other frame images inorder staring from its adjacent frame image, whereby the productrecognition process is performed on the respective frame images. Thiscan reduce the computation and enables high-speed processing.

The processes at Step S113 and thereafter are the same as those in thefirst embodiment and therefore explanation thereof is omitted here.

According to the third embodiment, the product recognition process isperformed based on the image without bones, and the image signalcomponent of the product in the recognized product region is attenuated.This can attenuate products with high accuracy. Further, the completeproduct recognition process is performed on only one image, namely, thechest image, and the simple product recognition process is performed onthe frame images. This can reduce the computation and enables high-speedprocessing. In this embodiment, both dynamic imaging and tomosynthesisimaging are performed on the same examination target site of the samesubject H. Hence, it is preferable that (i) the dynamic image beforeanalysis, (ii) the image of the analysis result of the dynamic image and(iii) the tomographic images obtained by performing the reconstructionprocess on the images obtained by tomosynthesis imaging are displayed bybeing arranged next to one another (arranging display), or two types ofthese images are displayed at the same position on the display unit 24switchably at proper timing (switchable display) or displayed on thedisplay unit 24 by being superimposed with different transmittances(superimposing display). This kind of display allows a user to makediagnosis by looking at the shape information and the functioninformation based on movement at the same time and comparing them withone another. Therefore, the user can accurately understand the state ofthe diseased site, and hence the diagnostic accuracy can be improved. Inthe arranging display or switchable display, for example, theinter-frame difference images or the like as the analysis result may bedisplayed as a video, and also the tomographic images obtained bytomosynthesis imaging may be displayed in the form of video. In thesuperimposing display, for example, the tomographic images obtained bytomosynthesis imaging may be superimposed on one image most clearlyreflecting the local motion extracted from the inter-frame differenceimages or the like as the analysis result so as to be displayed in theform of video; on the contrary, the inter-frame difference images or thelike as the analysis result may be superimposed on one image showing theshape characteristics most extracted from the tomographic imagesobtained by tomosynthesis imaging so as to be displayed as a video. Thismakes it easy for a user to compare the shape information and thefunction information at the same position in the same examination targetsite with one another. Therefore, the user can accurately understand thestate of the diseased site. Further, the result of a CAD process usedfor cancer diagnosis support or the like performed on the tomographicimages obtained by tomosynthesis imaging and the analysis result of thedynamic image, such as the image(s) in which the inter-frame differencevalues are shown in color, may be displayed by being arranged next toone another, displayed at the same position on the display unit 24switchably at proper timing or displayed on the display unit 24 by beingsuperimposed with different transmittances.

For both dynamic imaging and tomosynthesis imaging, preferably,alignment is made such that the radiation emission direction at thecenter point of radiation radially emitted from the radiation source 11matches the normal line of the FPD cassette 4 extended from the centerpoint of the imaging region of the FPD cassette 4. However, in thevisiting system (100), the FPD cassette 4 and the radiation generationapparatus 1 are separate. Hence, it is difficult for a user toaccurately make such alignment and the accurate alignment requires time.Then, at least three three-dimensional magnetic sensors are provided,for example, each of inside the FPD cassette 4 and near the radiationexit of the radiation source 11 so that the visiting system can detectthe position of the FPD cassette 4, the angle thereof to the horizontalsurface, the position of the radiation exit of the radiation source 11,and the radiation emission direction; and with a not-shown drivemechanism provided in the radiation generation apparatus 1, move/changethe position and direction of the radiation generation apparatus 1, tobe specific, the position and direction of the radiation source 11, suchthat the radiation emission direction at the center point of radiationradially emitted from the radiation source 11 matches the normal line ofthe FPD cassette 4 extended from the center point of the imaging regionof the FPD cassette 4. Further, the radiation generation apparatus 1 maybe provided with a not-shown aperture stop part to reduce the irradiatedfield of radiation at the radiation exit of the radiation source 11 andfurther provided with a drive mechanism to change the irradiated fieldof radiation, whereby the irradiated field of radiation is changed toapproximately match the imaging region of the FPD cassette 4. Further,the detected position of the FPD cassette 4, angle thereof to thehorizontal surface, position of the radiation exit of the radiationsource 11 and radiation emission direction may be displayed on thedisplay unit 24 of the console 2 so that a user can recognize in whatdirection and how much the position and direction of the radiationgeneration apparatus 1, to be specific, the position and direction ofthe radiation source 11, should be moved/changed. Further, it may bedetermined whether the radiation emission direction at the center pointof radiation radially emitted from the radiation source 11 approximatelymatches the normal line of the FPD cassette 4 extended from the centerpoint of the imaging region of the FPD cassette 4, and the determinationresult may be displayed on the display unit 24 of console 2.

This can shorten time necessary for a user to accurately align the FPDcassette 4 with the radiation source 11, and this accurate alignment canreduce (i) unnecessary exposure of a subject H to radiation and (ii)decrease in image data quality.

For tomosynthesis imaging of a subject H who is at a reclining position,in general, the radiation generation apparatus 1 requires a complexdrive mechanism to move the radiation source 11 to be accurately alignedwith the FPD cassette 4 if the FPD cassette 4 is not horizontallyplaced. In order to simplify the drive mechanism of the radiationgeneration apparatus 1 used for the radiation source 11 at the time oftomosynthesis imaging, how much the FPD cassette 4 inclines with respectto the horizontal surface may be detected with the above-describedthree-dimensional magnetic sensors or the like, whether the FPD cassette4 is approximately horizontally placed may be determined, and thedetermination result may be displayed on the display unit 24 of theconsole 2. The angle indicating how much the FPD cassette 4 inclineswith respect to the horizontal surface is also an indicator of theposture of the subject H. Hence, parameters or the like for dynamicanalysis and for the reconstruction process performed on the imagesobtained by tomosynthesis imaging may be changed according to thedetected angle.

In tomosynthesis imaging, an image of a section near an isocenter C,namely, the rotation center of the radiation source 11 moving intomosynthesis imaging (shown in FIG. 7B), in the z direction has theminimum amount of artifacts. Hence, in order that a user can positionthe most interesting part of the examination target site of a subject Hat the isocenter C at the time of tomosynthesis imaging, preferably, asshown in FIG. 7A, the radiation generation apparatus 1 emits, inadvance, LED laser beams LB or the like to a subject H so as to projectlight or the like so that a user can recognize the position of theisocenter C in advance as shown with CP in FIG. 7C. This allows a userto easily position the most interesting part of the examination targetsite of a subject H near the isocenter C at the time of tomosynthesisimaging.

If the range, within which tomographic images are generated byperforming the reconstruction process on the images obtained bytomosynthesis imaging, is different from the range desired by a user, animage of a desired section (a desired tomographic image) cannot beobtained; or an image of an excessive section is generated, andaccordingly the reconstruction process unnecessarily takes muchprocessing time, and also the data amount increases and the storagecapacity is unnecessarily consumed. Then, in order that a user canperform, at the time of tomosynthesis imaging, the above-describedpositioning or change the parameters for the reconstruction process suchthat the range, within which tomographic images are generated by thereconstruction process, matches the range desired by the user,preferably, as shown in FIG. 7A, the radiation generation apparatus 1emits, in advance, LED laser beams LB or the like to the range, withinwhich tomographic images are generated by the reconstruction process, ofa subject H so as to project light or the like so that a user canrecognize the range in advance as shown with R in FIG. 7C. This allows auser to perform the positioning or change the parameters for thereconstruction process such that only tomographic images within theinteresting range of the examination target site of a subject H aregenerated at the time of tomosynthesis imaging, and accordingly canincrease examination efficiency.

FIG. 7A shows a state, viewed from the top, in which the radiationgeneration apparatus 1 emits the laser beams LB to, of a subject H, apoint corresponding to the isocenter C and the range R within whichtomographic images are generated by the reconstruction process. FIG. 7Bshows the state in FIG. 7A from a side opposite to a side where theradiation generation apparatus 1 is disposed, wherein the positionalrelationship of the subject H, the radiation generation apparatus 1 andthe FPD cassette 4 is shown. FIG. 7C shows the subject H in the state inFIG. 7A from the side where the radiation generation apparatus 1 isdisposed.

Preferably, near the radiation exit of the radiation source 11, there isprovided a sensor which measures distance from the radiation exit to thesurface of a subject H in a noncontact manner, such as an ultrasonicdistance sensor or an infrared sensor which is constituted ofinfrared-ray emitting elements and light receiving elements, and detectsthe reflected light of light output from the emitting elements with thereceiving elements and converts the detected light into a distance byevaluation and mathematical operation on the light, and the console 2has a function of estimating a dose rate or an incident dose on thesurface of the subject H based on the distance from the radiation exitto the surface of the subject H (FSD: Focal spot to Skin Distance)measured by the sensor and the radiation emission conditions to be sentto the radiation emission control unit 12. Attaching this dose rate orincident dose to the taken image data and storing them together enablesdose management about how much the subject H is exposed. Preferably, theconsole 2 performs control to prohibit the radiation generationapparatus 1 from emitting radiation if the calculated estimated value ofthe dose rate or incident dose on the surface of a subject H is equal toor more than a predetermined threshold value. This can prevent radiationof a predetermined dose rate or incident dose or more from being emittedto a subject H, caused by, for example, the subject H and the radiationexit being too close to each other.

Preferably, the console 2 further has a function of: measuring distancefrom the radiation exit to the FPD cassette 4 (SID: Source to ImageDistance) based on the position of the FPD cassette 4 and the positionof the radiation exit of the radiation source 11 detected by thethree-dimensional magnetic sensors or the like provided near theradiation exit of the radiation source 11 and in the FPD cassette 4;detecting the size of the irradiated field from the not-shown aperturestop part to reduce the irradiated field of radiation provided at theradiation exit of the radiation source 11; and estimating an incidentsurface dose with a formula of the NDD (numerical dose determination)method or the like based on (i) the FSD and (ii) the radiation emissionconditions to be sent to the radiation emission control unit 12, whichare described above, (ii) the measured SID and (iv) the detected size ofthe irradiated field. Further, the console 2 may calculate bodythickness information on a subject H by subtracting FSD from SID, whichare measured as described above, and, based on the calculated bodythickness information, calculate the radiation emission conditions to besent to the radiation emission control unit 12. This enables radiationemission under the radiation emission conditions suitable for the bodythickness of a subject H and accordingly can reduce decrease in imagequality due to an insufficient dose and unnecessary increase in exposureof the subject H to radiation due to an excessive dose.

Preferably, the console 2 attaches the SID and FSD measured by thesensors or the like and the radiation emission conditions to the takenimage data and store them together; and if a subject H has been imagedpreviously by this visiting system and the previously taken image datais stored in the console 2, reads the SID, FSD and radiation emissionconditions attached to the previously taken image data and sends theread radiation emission conditions to the radiation emission controlunit 12, and also moves/changes the position and direction of theradiation generation apparatus 1, to be specific, the position anddirection of the radiation source 11, with the not-shown drive mechanismprovided in the radiation generation apparatus 1 in such a way as toagree with the read SID and FSD. This allows a user to accuratelyreproduce the alignment and the radiation emission conditions used inthe previous imaging and accordingly easily compare the recently takenimage with the previously taken image(s), whereby a dynamic image moreeasily comparable with the previously taken image(s) can be obtained.

Fourth Embodiment

In the first to third embodiments, in order to improve the diagnosticaccuracy based on dynamic images, in a dynamic image, the image signalcomponents of products, which are obstructive to dynamic diagnosis, areattenuated, and the dynamic image with the attenuated image signalcomponents of the products is displayed for dynamic analysis. Meanwhile,there is a demand for checking whether products are properly inserted.It is difficult to perform the check by displaying a dynamic image as itis without the product attenuation process because products such as alead of a heart pacemaker and a catheter show low contrast on an X-rayimage. Hence, in a fourth embodiment of the present invention, when thedynamic image is displayed as with the first to third embodiments, aproduct-enhanced image is generated and displayed together.

The dynamic analysis system 100 of the fourth embodiment is, inconfiguration, the same as that of each of the first to thirdembodiments except that, in the fourth embodiment, the dynamic analysissystem 100 can further perform still image shooting (simpleroentgenography).

The console 2 can set radiation emission conditions for still imageshooting in addition to the radiation emission conditions for dynamicimaging. Before or after dynamic imaging, an operator operates theoperation unit 23 to set the conditions for still image shooting in theconsole 2, and the imaging is performed.

A chest plain radiograph obtained by still image shooting is subjectedto a product enhancement process performed in the console 2 by thecontrol unit 21 in cooperation with a program stored in the storage unit22 so as to generate a product-enhanced image. As a method for theproduct enhancement process, a well-known image processing technologycan be used. For example, a chest plain radiograph is subjected tosmoothing with a median filter and sharpening by unshape masking, andthe obtained image is subjected to banalization by thresholding usingthe moving average method (“Improved Visualization of Cardiac PacemakerLead on Chest Radiographs”, Radiological Physics and Technology, Vol.63, No. 4, pp. 420-427) or the like.

The product-enhanced image is, by the control unit 21, correlated andstored in the storage unit 22 with a dynamic image which is takentogether with the chest plain radiograph, and displayed on the displayunit 24. For example, the product-enhanced image may be displayed, atStep S12 in the first to third embodiments, together with the dynamicimage after (or before and after) the product attenuation process.Alternatively, an operation button for displaying a product-enhancedimage or the like may be displayed on the display unit 24, and theproduct-enhanced image may be displayed in response to an operation onthe operation button through the operation unit 23.

Thus, in the fourth embodiment, a dynamic image with attenuated productsis displayed. This allows a user to observe the ventilation state duringor after a surgery without being affected by products. Further, in thefourth embodiment, a dynamic image is displayed together with aproduct-enhanced image. This allows a user to easily check whetherproducts are properly inserted.

Further, pulse emission for dynamic imaging may cause malfunctions of apacemaker, an implantable cardiac defibrillator or the like (hereinafter“a pacemaker(s) or the like”). Hence, continuous emission needs to beused to image patients who use pacemakers or the like. If patientinformation shows YES in “pacemaker or the like”, or a pacemaker or thelike is recognized in the lung field region by still image shooting(scout shooting) performed immediately before dynamic imaging or byanalysis of one to several frame images taken immediately after dynamicimaging starts by pulse emission, it is preferable to display on theconsole 2 a message to prohibit or stop dynamic imaging by pulseemission. This can avoid malfunctions of a pacemaker or the like at thetime of imaging a patient who uses a pacemaker or the like. When apacemaker or the like is recognized by analysis of one to several frameimages taken immediately after dynamic imaging starts by pulse emission,the console 2 may send a signal to stop radiation emission to theradiation generation apparatus 1, thereby stopping radiation emission,or may send a signal to change to continuous emission to the radiationgeneration apparatus 1, thereby changing to continuous emission whichautomatically makes the exposure dose uniform.

If the radiation generation apparatus 1 can perform both pulse emissionand continuous emission, it is preferable that pulse emission, whichcauses little blurring in frame images, is automatically selected whenmotion of the target site of a subject H is relatively slow, dynamicimaging is performed at a low frame rate and the taken dynamic image isanalyzed. This can prevent, in frame images, blurring caused bymovements and enables shaper depiction of a fine target even when theframe rate is low. On the other hand, if motion of the target site of asubject H is relatively fast and dynamic imaging is performed at a highframe rate, the FPD cassette 4 may be configured to repeat only readingwithout having the accumulation time, and the radiation generationapparatus 1 may be configured to perform continuous emission as theradiation emission method. Elimination of the accumulation time of theFPD cassette 4 realizes a high frame rate as compared with pulseemission for which the accumulation time is ensured.

As described in the first to fourth embodiments, according to thedynamic analysis system 100, the control unit 21 of the console 2performs the attenuation process to attenuate an image signalcomponent(s) of a product(s) in a plurality of frame images showing adynamic state of a subject H generated by the radiation generationapparatus 1 and the FPD cassette 4 working together, and analyzes thedynamic state of the subject H based on the frame images after theattenuation process.

Consequently, there is no difficulty in determining whether differencebetween analysis results of dynamic images shows change in the state ofa patient or shows presence/absence of a product(s). Accordingly, thediagnostic accuracy based on analysis results of dynamic images can beimproved.

The contents described in the above embodiments are preferred examplesof the dynamic analysis system of the present invention, and hence thepresent invention is not limited thereto.

For example, in the above embodiments, the dynamic analysis system is avisiting system (i.e., a system for going the rounds). However, thepreset invention is also applicable to a dynamic analysis system whichperforms dynamic imaging at a radiation room and analyzes the obtaineddynamic image(s).

Further, in the above embodiments, the console 2 sets the radiationemission conditions for still image shooting and dynamic imaging.However, it is possible that the radiation emission control unit 12 ofthe radiation generation apparatus 1 sets the radiation emissionconditions for still image shooting and dynamic imaging in advance, theexposure switch 13 is provided with separate switches for still imageshooting and dynamic imaging, and when the switch for still imageshooting is pressed, exposure (radiation emission) is performed underthe radiation emission conditions for still image shooting, whereas whenthe switch for dynamic imaging is pressed, exposure is performed underthe radiation emission conditions for dynamic imaging. Thisconfiguration enables quick switching between still image shooting anddynamic imaging and also can reduce occurrence of wrong exposure causedby setting the radiation emission conditions for still image shootinginstead of the radiation emission conditions for dynamic imaging bymistake, or vice versa.

Further, in the above embodiments, the radiation emission conditions areread from the storage unit 22 and set in the radiation emission controlunit 12 through the communication unit 25. However, it is possible thatthe radiation generation apparatus 1 has not-shown storage unit, displayunit and operation unit, and the radiation emission conditions stored inthe storage unit of the radiation generation apparatus 1 are displayedon the display unit of the radiation generation apparatus 1 andselected/corrected through the operation unit of the radiationgeneration apparatus 1 and then set in the radiation emission controlunit 12. In this case, the set radiation emission conditions may be sentfrom the radiation generation apparatus 1 to the console 2 through thecommunication unit 25.

Alternatively, it is possible that, without sending/receiving of the setradiation emission conditions through the communication unit 25, the FPDcassette 4 detects radiation emitted from the radiation generationapparatus 1 and determines, based on the dose rate or pixel value(s) ofa frame image(s) immediately after start of radiation emission (i.e.,irradiation), whether the detected radiation is for still image shootingor dynamic imaging, and, according to the determined information,namely, still image shooting or dynamic imaging, automatically changesthe image reading conditions, such as a frame rate, the number of frameimages taken by each imaging, an image size (matrix size), sensitivity(gain), a binning number and radiation-emission waiting time,immediately after start of radiation emission, and obtains frame imagesunder the changed image reading conditions. In this case, whendetermines that the detected radiation is for still image shooting, theFPD cassette 4 sets or changes the image reading conditions to be asmall gain, no binning and a radiation-emission waiting time of 0.5 toseveral seconds to perform reading only one time, whereas whendetermines that the detected radiation is for dynamic imaging, the FPDcassette 4 sets or changes the image reading conditions to be a largegain, binning of several to several ten pixels and a radiation-emissionwaiting time of 0 to 50 milliseconds to repeatedly performradiation-emission waiting and reading by returning to theradiation-emission waiting time after reading each frame image. If thedetermined information by the FPD cassette 4, namely, still imageshooting or dynamic imaging, mismatches the current image readingconditions, the FPD cassette 4 may notify the console 2 about thesituation, and the console 2 may display thereon, immediately afterstart of radiation emission, a message to stop imaging because theradiation emission conditions mismatch the image reading conditions.

Usually, still image shooting and dynamic imaging are different in doserate, and the dose rate for dynamic imaging is much smaller than thatfor still image shooting. Hence, the FPD cassette 4 can identify,immediately after start of radiation emission, still image shooting ordynamic imaging based on the dose rate of emitted radiation or the pixelvalue(s) of a frame image(s). Further, the FPD cassette 4 can identify,immediately after start of radiation emission, still image shooting ordynamic imaging by detecting rising characteristics of the dose rate(changing speed of the dose rate) of emitted radiation too. As adetection unit for the dose rate, for example, an exposure sensor whichoutputs the output value in proportion to the dose of the emittedradiation is provided on the back surface of a glass substrate in theFPD cassette 4, and the FPD cassette 4 reads the output value of thesensor at predetermined time intervals of, for example, several toseveral hundred microseconds. Then, the FPD cassette 4 calculates thedose rate from the change amount of the output value of the sensor readat the predetermined time intervals. The FPD cassette 4 can alsocalculate the changing speed of the dose rate from the dose ratecalculated at predetermined time intervals. The FPD cassette 4 firstdetects that the obtained output value of the sensor exceeds apredetermined threshold value, thereby detecting that a predeterminedradiation dose is emitted, and then identifies still image shooting ordynamic imaging by determining whether or not the calculated dose rateor changing speed of the dose rate is equal to or more than apredetermined threshold value, for example.

The FPD cassette 4 may identify still image shooting or dynamic imagingand further identify dynamic imaging by pulse emission or dynamicimaging by continues emission based on (i) the value of the dose rateand (ii) a period of time that the dose rate keeps being a predeterminedthreshold value or more or (iii) a period of time that the dose ratebecomes almost 0 from the predetermined threshold value, and set theimage reading conditions according to the identification result(s). Forexample, the FPD cassette 4 determines that it is dynamic imaging bycontinuous emission if the dose rate is less than a predeterminedthreshold value; determines that it still image shooting if (i) the doserate is equal to or more than the predetermined threshold value, (ii)the period of time that the dose rate keeps being the predeterminedthreshold value or more is equal to or more than a predetermined periodof time, or (iii) the product of the dose rate multiplied by the periodof time that the dose rate keeps being the predetermined threshold valueor more is equal to or more than the predetermined threshold value isequal to or more than a predetermined threshold value; and determinesthat it is dynamic imaging by pulse emission if none of the above issatisfied. Preferably, the threshold values used here are changedaccording to the patient information such as the build, age and sex. Forexample, if a patient is thin or a child, and the dose rate emitted(output) from the radiation generation apparatus 1 does not change, thethreshold value is set at a large value. The FPD cassette 4 may detecttiming at which the dose rate becomes almost 0 from the predeterminedthreshold value and thereby detect timing of the end of still imageshooting or dynamic imaging by pulse emission. The FPD cassette 4 mayidentify still image shooting or dynamic imaging by detecting the pixelvalue(s) of a frame image(s). In this case, the FPD cassette 4, forexample, keeps obtaining frame images at a predetermined frame ratesince before radiation emission, and detects that the representativevalue of pixel values of all of or some of the obtained frame imagesexceeds a predetermined threshold value, thereby detecting that apredetermined radiation dose is emitted, and estimates the dose ratefrom the representative value. Thus, the FPD cassette 4 identifies stillimage shooting or dynamic imaging.

Here, the FPD cassette 4 identifies still image shooting or dynamicimaging. However, it is possible that immediately after start ofradiation emission, the FPD cassette 4 sends the dose rate, the changingspeed of the dose rate, the frame images or the representative value ofthe pixel values of the frame images to the console 2 through thecommunication unit 25, and the console 2 identifies still image shootingor dynamic imaging, and sends the image reading conditions according tothe identified information, namely, still image shooting or dynamicimaging, to the FPD cassette 4 through the communication unit 25 so asto set the image reading conditions therein. This configuration makes itpossible that, without sending/receiving of the radiation emissionconditions between the radiation generation apparatus 1 and the console2 or the FPD cassette 4, the console 2 or the FPD cassette 4 identifies,immediately after start of radiation emission, still image shooting ordynamic imaging based on the radiation emitted by the radiationgeneration apparatus 1, and sets the image reading conditions suitablefor the FPD cassette 4 to obtain frame images. Therefore, even if theradiation generation apparatus 1 and the console 2 or the FPD cassette 4cannot communicate with one another because their makers are differentor so, the FPD cassette 4 can quickly switch between still imageshooting and dynamic imaging without trouble, only by the radiationgeneration apparatus 1 changing the radiation emission conditions.Further, a message to stop imaging because the radiation emissionconditions mismatch the image reading conditions may be displayed on theconsole 2, which can protect patients from being unnecessarily exposed.

Further, the access point 3 may have a function ofcommunicating/connecting to a 3G line, a 4G line, a satellitecommunication line or the like and connecting to a mobile phone network,Internet or the like via the above wireless communication line andtransferring the image data, analysis results calculated based on imagedata, patient information on subjects H and so forth which are stored inthe storage unit 22 of the console 2 and encoded and/or compressed,directly from the visiting system to a server on a cloud or a server orterminal such as a PACS in a remotely located hospital. The console 2can receive, through the operation unit 23 or the communication unit 25,vital information on subjects H such as the respiratory rate, heart rateand blood pressure and/or measurement results of other examinations onthe subjects H such as the oxygen saturation, respiratory flow andelectrocardiograms, and the access point 3 may also have a function oftransferring these vital information and/or measurement results of otherexaminations which are input into the console 2 and attached to theimage data. Thus, the visiting system is configured to send the imagedata, to which the patient information, vital information, measurementresults of other examinations and/or analysis results are attached,directly to a remotely located facility such as a hospital so as to beviewed there. Hence, when this visiting system is used at the scene ofaccidents, disasters, emergencies or the like, and takes images,calculates analysis results based on the taken image data, and obtainsand receives vital information and/or measurement results of otherexaminations, even if no doctor who can make diagnosis based on thesedata and information is at the scene, a doctor who is far away from thescene can make remote diagnostics immediately by viewing these data andinformation, and treatments or the like can be speedily performed on thesubjects H at the scene based on the diagnosis results made by the rightdoctor. At the time, if speediness has priority, preferably, thecompression method is changed depending on the communication capacityper unit time of the wireless communication line. For example, if thecommunication capacity is small, the compression rate is increased toreduce the data amount, irreversible compression is employed, or thelike.

Further, in the above embodiments, the access point 3 is movablyinstalled in the visiting system. However, there may be a plurality ofaccess points 3, and in this case, some or all of the access points 3may be immovably installed in a hospital or the like.

Further, in the above embodiments, the communication unit 25 includes awireless LAN adopter or the like and controls data sending/receivingto/from external apparatuses such as the radiation generation apparatus1 and the FPD cassette 4 connected to a communication network such as awireless LAN via the access point 3. However, the console 2 may beconfigured such that the communication unit 25 directly sends/receivesdata to/from some or all of the external apparatuses using an ad hocmode of a wireless LAN, Bluetooth® or the like, not via the access point3. This configuration omits some or all of the access points 3 andaccordingly can reduce the weight of the system and also reduce thecosts.

Further, for the FPD cassette 4 to send obtained frame images to theconsole 2 through the communication unit 25 via a wireless or cablenetwork, depending on the communication capacity per unit time, eachtime the FPD cassette 4 obtains a frame image during dynamic imaging,the FPD cassette 4 may temporarily store the frame image in the storageunit thereof, and also perform data thinning in terms of space and/ortime on the frame image and send the thinned frame image data to theconsole 2 in almost real time, and the console 2 may display the frameimage data received from the FPD cassette 4 on the display unit 24 inalmost real time. In this case, when dynamic imaging finishes, the FPDcassette 4 may send, to the console 2, all the frame image data beforedata thinning or the frame image data which is not sent to the console 2yet, the date being stored in the storage unit of the FPD cassette 4.This enables control to display, on the display unit 24, the frame imageobtained by the FPD cassette 4 in almost real time during dynamicimaging even if the communication capacity per unit time is small due touse of a wireless network or the like. Thereby, a user such as aradiologist can quickly grasp the abnormal state of imaging from theframe image displayed on the display unit 24 and hence can determine tostop imaging, which can protect patients from being unnecessarilyexposed when imaging is abnormal.

There is a case where during reading by the FPD cassette 4,electromagnetic waves (noise caused by environment) emitted from avisiting or portable radiation generation apparatus or a treatmentapparatus such as a high-frequency treatment apparatus placed around theFPD cassette 4 are applied to the FPD cassette 4, and artifacts occur inthe image data read from/by the FPD cassette 4. Hence, preferably, theFPD cassette 4 or the console 2 detects, before or during imaging,electromagnetic waves and frequency characteristics thereof in thevicinity of the FPD cassette 4, and estimates, based on the detectedfrequency characteristics, a spatial pattern (spatial frequency) ofartifacts such as streaks occurring on the image data, and the FPDcassette 4 or the console 2 performs an image correction process on theobtained frame images so as to attenuate the artifacts of the estimatedspatial pattern. The artifact estimation and the correction process canimprove the diagnostic accuracy based on analysis results of dynamicimages.

In the above, a hard disk, a nonvolatile semiconductor memory or thelike is used as a computer readable medium of the programs of thepresent invention. However, this is not a limitation. As the computerreadable medium, a portable storage medium such as a CD-ROM can be used.Further, as a medium to provide data of the programs of the presentinvention, a carrier wave can be used.

The detailed configurations and actions of the apparatuses or the likeconstituting the dynamic analysis system can also be appropriatelymodified within a range not departing from the spirit of the presentinvention.

What is claimed is:
 1. A dynamic analysis system that analyzes aplurality of frame images showing a dynamic state of a chest of asubject, comprising: an operation unit to select a region in a lungfield region of the subject; and an analysis unit that calculates acharacteristic amount of indicating a local motion in the lung fieldregion, wherein the analysis unit calculates, based on the selectedregion and the calculated characteristic amount, a ratio of thecharacteristic amount in an unselected region except the selected regionfrom the lung field region that is an entire lung field region to thecharacteristic amount in the entire lung field region.
 2. The dynamicanalysis system according to claim 1, wherein the characteristic amountindicating the local motion in the lung field region is thecharacteristic amount indicating a ventilation function or a bloodstreamfunction in the lung field region.
 3. The dynamic analysis systemaccording to claim 1, wherein the characteristic amount indicating thelocal motion in the lung field region is the characteristic amountindicating local signal change in the lung field region.
 4. The dynamicanalysis system according to claim 3, wherein the characteristic amountindicating the local signal change in the lung field region is aninter-frame difference value, and the analysis unit calculates a ratioof an integrated value of the inter-frame difference value of theunselected region except the selected region from the entire lung fieldregion to an integrated value of the inter-frame difference value of theentire lung field region.
 5. The dynamic analysis system according toclaim 1, further comprising a display unit that displays an analysisresult based on the ratio calculated by the analysis unit.